This invention relates to an apparatus for processing semiconductor wafers or glass photomask plates, and more particularly, to a direct drive motor assembly for a semiconductor wafer processing system that improves the processing yield of semiconductor wafers.
In the production of integrated circuits, the semiconductor wafers or substrates from which the integrated circuit chips are cut are processed through multiple steps. The basic material for the substrates on the wafers may be silicon, glass, or ceramic materials of various sorts or other similar materials of very thin wafer-like configuration. This basic substrate is subjected to coating, etching, and cleaning processes and it is extremely important that each processing step is performed with the greatest possible yield allowing a decrease in production costs.
Semiconductor wafers and glass photomask plates have been processed by spinning them about a vertical axis where the wafers or masks are stacked vertically as described in U.S. Pat. No. 3,760,822 with various holding mechanisms such as vacuum chucks. This has led to further disadvantages where the wafer may be only processed on one side at a time without a significantly different processing rate, wherein the topside processes at a much faster rate than that of the underside.
Other processing devices such as described in U.S. Pat. No. 3,970,471, process each wafer individually. Although the wafer is rotated about a horizontal axis, such a device only can process a single wafer at each station and is expensive and time consuming.
To eliminate many of the problems noted above, the assignee of the present invention developed a wafer processing system and set forth and claim the system in U.S. Pat. No. 4,300,581, titled "Centrifugal Wafer Processor", issued Nov. 17, 1981. The invention set forth therein permits the processing of a plurality of wafers at the same time in a carrier. In accordance with that invention, semiconductor wafers or glass photomask plates are processed by inserting into them into the carrier and placing the carrier in a rotor, which rotates around a substantially horizontal axis. Various fluids may be applied to the wafers uniformly through the spray nozzles while the wafers are being rotated.
The foregoing system includes built-in shock absorbers that extend vertically from a frame that supports a bowl into which the carrier is inserted. The shock absorbers assist in reducing the transfer of vibrational energy to the carrier. The reduction of vibration energy transfer facilitates a greater processing yield since the wafers are not subject to damaging mechanical stresses and strains. The present inventors have recognized a further manner in which to reduce the vibration energy transfer using a direct drive motor assembly having one or more shock absorbing structures associated therewith.
A still further problem present in the prior apparatus is the sealing of the motor to isolate it from exposure to materials, such as processing fluids. The present inventors have provided a unique solution to this problem by providing an aggressive seal about the rotor of the motor.